1. Field of the Invention
The present invention relates to an ink jet recorder for recording images etc., on recording media with ejected ink, and more specifically relates to an ink jet recorder having a purging device for purging the recording head and a flushing device for removing air bubbles inside the recording head.
2. Description of the Related Art
Ink jet printers have been typically known as ink jet recorders for use in recording characters, images etc., on recording media such as paper etc., with ejected ink.
As shown in FIG. 8, a typical ink jet printer uses an ink cartridge P1 for storage of ink which can be removably mounted in a recording head unit P3 having a recording head P2, so that ink cartridge P1 is attached to recording head P2 by mounting it to recording head unit P3. The mounted ink cartridge P1 supplies recording head P2 with ink, which in turn is ejected from an ejection nozzle P4 provided in recording head P2, thus performing printing of characters etc. Provided inside recording head P2 is ink channels (not shown) which are defined with side-walls made up of piezoelectric elements so that ink compressed by the alternation of the intra-channel volume will be ejected from nozzle P4.
When predetermined conditions are satisfied during the operation of the ink jet printer, for example, automatically or by user interaction, ejecting nozzle P4 is subjected to a so-called purging operation, by which ink inside nozzle P4 is sucked from the ejection side of ejecting nozzle P4, that is, nozzle tip P5 having openings or ejection holes (not shown).
The specific operation of purging comprises: covering nozzle tip P5 with a suction cap P6; applying a negative pressure within suction cap P6 by an unillustrated suction pump; and sucking the ink from ink cartridge P1 and recording head P2 by way of suction cap P6 so as to displace the ink to the outside.
This purging operation is performed when an unused ink cartridge P1 is replaced or initially attached, in order to initially introduce the ink inside unused cartridge P1 into recording head P2. Alternatively, it is also performed in order to prevent mal-ejection of ink during the operation of the ink jet printer. A purging operation for the former purpose in particular is referred to as an initial purge or initial ink introduction purge.
When the user has mounted an unused ink cartridge P1 as a replacement or for initial setup, air will enter recording head P2. More specifically, there is a commutation passage between the ink feed port on the ink cartridge P1 and the ink inlet port on the recording head P2, and air will enter this commutation passage when ink cartridge P1 is mounted into recording head P2.
In a typical configuration, a filter is provided at the ink inlet port of recording head P2, aimed mainly at the prevention of foreign substances entering recording head P2.
Accordingly, when the aforementioned purging operation (initial purge) is performed after replacement of an ink cartridge P1 so that ink is rapidly sucked from the nozzle tip P5 of ejection nozzle P4 by means of suction cap P6, air within the aforementioned commutation passage rushes in and passes through the filter attached at the ink inlet port of recording head P2, generating a number of air bubbles. The air bubbles rapidly mix with the ink inside recording head P2, resultantly leaving air bubbles inside the ink channels and ejection nozzle P4.
In general, when ink jet printers of this type are shipped from the factory, recording head P2 is charged with a liquid for preservation (to be referred to as a storage solution) having properties similar to the ink but containing no pigment and dye.
For this reason, also when the aforementioned purging operation is performed after the user has initially attached an ink cartridge P1 to recording head P2, air inside the aforementioned commutation passage rushes in and passes through the filter attached at the ink inlet port of recording head P2, and the air rushes in and mixes with the ink inside recording head P2, resultantly generating a great deal of air bubbles and hence leaving the air bubbles inside the ink channel and ejection nozzle P4.
In ink jet printers of this type, there are cases where ink cartridge P1 has a filter at its ink feed port. This filter prevents entrance of foreign substances inside cartridge P1 into recording head P2 and also prevents ink leakage by making use of the surface tension of ink acting on the pores of the filter. Also in this case, when, upon the implementation of purging, ink inside ink cartridge P1 rushes through the filter provided at the ink feed port, into the aforementioned commutation passage containing air, a great number of air bubbles will be generated, resultantly leaving the air bubbles inside the ink channels and ejection nozzle P4.
Air bubbles remaining inside the ink channels and ejection nozzle P4 hinder the increase in pressure for ink to be ejected out, causing mal-ejection and hence degradation of recording image.